A light emitting diode (LED) is a semiconductor material impregnated, or doped, with impurities. These impurities add “electrons” and “holes” to the semiconductor, which can move in the material relatively freely. Depending on the kind of impurity, a doped region of the semiconductor can have predominantly electrons or holes, and is referred as n-type or p-type semiconductor regions, respectively. In LED applications, the semiconductor includes an n-type region and a p-type region. A reverse electric field is created at the junction between the two regions, which cause the electrons and holes to move away from the junction to form an “active region.” When a forward voltage sufficient to overcome the reverse electric field is applied across the p-n junction, electrons and holes are forced into the active region and combine. When an electron combines with a hole, it falls to a lower energy level and releases energy in the form of light.
The light emission profile from an LED is non-directional and typically assumes a “lambertian” like profile where light is equally emitted into all directions. However, in many applications, only focused light is useful. Typically, secondary optics are required to capture and shape a larger portion of the total available light from the LED. These secondary optics are costly and increase the size of the overall package carrying the LED.
Accordingly, it would be desirable to shape the emission profile from an LED such that the emitted light can more readily be used without external complicated and costly secondary optics.